The goal of this research is to develop new compounds for the treatment of AIDS. Our approach to chemotherapy stems from earlier work, which showed that replication and expression of Rous sarcoma virus could be inhibited in tissue culture by means of hybridization of an oligonucleotide complementary to a segment of the RSV genome. This novel type of chemotherapy became potentially applicable to AIDS, after the HIV genome had been sequenced. The feasibility of the approach was greatly enhanced by the development of solid phase synthesis. At this point in 1985, we formed a cooperative group with Dr. Gallo, a pioneer in AIDS discovery, and Dr. Letsinger, father of the solid phase synthetic method, to combined our backgrounds in the interests of a new form of chemotherapy for AIDS. During the earlier years of this grant, we synthesized and tested unmodified oligonucleotides, complementary to conserved segments of the viral genome, which showed promise as inhibitors of HIV replication and expression in tissue culture. Degradation of the oligomers by intracellular enzymes, however, made it desirable to make nuclease resistant modifications. the ID50 was enhanced from the 10-5 M to the 10-7 - 10-8 molar range in this latter way. We have recently explored the toxicity (rather low) and the pharmacokinetics (widespread distribution) of the oligodeoxynucleotide phosphorothioates in particular. We have continued to make backbone modifications of oligomers which, hopefully, have a) nuclease resistance; b) enhanced hybridization association constants; and c) RNase H sensitivity. Good progress has been made along these lines. The cholesteryl-conjugated oligodeoxynucleotide phosphorothioate shows particular promise. We are also scaling up synthesis from the multimilligram to the 5-40 gram level, using, in part, certain techniques worked out here. These larger amounts of our selected, most efficacious oligomers make it possible to implement studies with animal model systems. Testing has already begun, in collaboration with Dr. Matthew Gonda at the Frederick Cancer Research Facility in a transgenic BIV mouse system. We are also preparing for animal retroviral inhibition testing under the aegis of Dr. Polly Sager, Director of the NIAID program on FELV, FIV, and simian animal models, which have characteristics similar to HIV.